1. Technical Field
The present invention relates to a resin cover removal structure and a resin cover. Specifically, the present invention relates to a resin cover removal structure that makes it possible to easily remove a resin cover attached to a metallic body, and a resin cover having the removal structure.
2. Related Art
There are many cases where a synthetic resin cover is attached to a part of a metallic body. For example, when the body is an engine of a vehicle, the engine body has a portion covered with a cover such as a cylinder head cover or a chain cover. The engine body is roughly divided into three components: a cylinder head, a cylinder block and a crankcase in the descending order in a piston movement direction. The cylinder head cover normally covers the upper surface of the cylinder head: The chain cover is provided so as to cover a chain bridged from a crankshaft of the crankcase to a camshaft of the cylinder head on a side surface of the engine body. In addition, the engine body has a portion to which a component such as an intake manifold or the like is similarly attached. In a portion where such a cover etc. is attached, normally the cover etc. is brought into close contact with the engine body with a gasket interposed therebetween, and is fixed by bolting.
When engine maintenance etc. is performed, it is necessary to remove the cover etc. However, a sealing material (gasket) is interposed between mating surfaces of the engine body and the cover etc., and the engine body and the cover etc. are normally firmly fixed together. Therefore, in removal of the cover etc., a bolt fastening the engine body and the cover etc. is removed, a flat tool such as a spatula is then inserted in a gap between the engine body and the cover etc, so that the cover etc. which is in close contact with the engine body with a gasket interposed therebetween is peeled off and removed from the engine body. However, a resin has come into use as a material of the cover etc., and it is necessary to prevent deformation and damage in removal from the engine body.
An attachment structure is known in which, for making it possible to easily remove an engine cover without damaging mating surfaces of the engine cover and an engine body, a special ring member is engaged with a shaft portion of a bolt for attaching a cylinder head cover to the engine body, so that the cover which is in close contact with the engine body is removed by lifting the cover as the bolt rises when the bolt is loosened (see, for example, Japanese Utility Model Publication No. 05-001637).
As described above, normally the engine body and the cover etc. are firmly fixed to each other with a sealing material interposed therebetween. Conventionally, in removal of the cover etc. from the engine body, a tool is inserted into a gap between mating surfaces thereof, so that the cover which is in close contact with the engine body is peeled off and removed from the engine body. However, there is a problem that during peeling operation, the mating surfaces of the cover and the engine body are often heavily wrenched by a tool, so that the cover is scratched. In particular, when the cover etc. is made of resin, the cover is easily damaged or deformed when removed.
An attachment structure as shown in Japanese Utility Model Publication No. 05-001637 has a problem that the cost increases because a separate ring-shaped member is used. For inserting the separate ring-shaped member, it is necessary to provide a gap in a portion where the separate ring-shaped member is interposed, and the separate ring-shaped member is required to have a strong force for lifting the cover as a bolt rises. Since the separate ring-shaped member is freely rotatable with respect to the bolt, noises may be caused by the separate ring-shaped member or the separate ring-shaped member may be detached by vibrations during operation of the engine, resulting in damage to the engine. Further, at the time of attaching the cover to the engine again or replacing the bolt, it is necessary to remove the separate ring-shaped member from the bolt, and when there are a large number of bolts for attaching the cover, enormous time and effort are required.
In particular, the chain cover is provided so as to cover a chain bridged from a crankshaft of a crankcase to a camshaft of a cylinder head as described above. Therefore, the chain cover is required to provide a seal across three components (cylinder head, cylinder block and crankcase) that make up the engine body. Thus, the chain cover is firmly fixed so as to secure sealing property even when there is a slight level difference between components, and it is difficult to remove the chain cover. Further, in the case of a V-type engine, a horizontally opposed engine or the like, the cylinder block and the cylinder head are branched, and therefore the chain cover for covering the side surface is inevitably enlarged, so that it is further difficult to remove the chain cover.